


Objects in Motion Tend to Stay in Motion

by the_deep_magic



Series: A Very Critical Role Kinktober 2020 [16]
Category: Critical Role (Web Series)
Genre: Exhibitionism, Fucking Machines, Kinktober 2020, M/M, Sex Toys
Language: English
Status: Completed
Published: 2020-10-19
Updated: 2020-10-19
Packaged: 2021-03-09 03:55:53
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,651
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27098458
Author URL: https://archiveofourown.org/users/the_deep_magic/pseuds/the_deep_magic
Summary: Day Sixteen: fucking machinesThey’re in the Whitestone workshop, where no one even thinks of bothering them, and Tary tries to ask as casually as possible. “So, Percy, let’s say you needed to power a single piston. The source needs to provide continuous, steady power for up to, let’s say, fifteen minutes, but a bare minimum of ten.”
Relationships: Taryon Darrington/Percival "Percy" Fredrickstein Von Musel Klossowski de Rolo III
Series: A Very Critical Role Kinktober 2020 [16]
Series URL: https://archiveofourown.org/series/1950748
Comments: 12
Kudos: 202





	Objects in Motion Tend to Stay in Motion

**Author's Note:**

> Listen: low-hanging fruit is the sweetest fruit. Gosh, this would’ve been so much easier if I knew a single fucking thing about engineering. Please ignore my incredibly rudimentary grasp of physics and accordingly shoddy technobabble.

The first model is powered by a wind-up crank, which works fantastically – for about three minutes. Tary gives it a shot, he really does, but it’s an exercise in frustration. Just when things are getting good, the damnable contraption slows down and dies. And logistically, there’s nowhere to put the crank that’s easily accessible while using it, even if Tary didn’t mind having to stop and wind it every few minutes.

The second version is steam-powered. The less said about it – and the burns on Tary’s ass – the better.

The lesson learned there is that heat is too dangerous a means to power such a device, which rules out several other of Tary’s ideas. He’s been working on the possibility of harnessing the power of gravity – by means of a pendulum, for example – but his research simply isn’t far enough along for this machine’s purposes. He tries to bounce some ideas off of Doty, but Doty is less than helpful.

The way he sees it, he has two options: give up on the thing entirely, or ask Percy for help. He asks Percy the next day.

They’re in the Whitestone workshop, where no one even thinks of bothering them, and Tary tries to ask as casually as possible. “So, Percy, let’s say you needed to power a single piston. The source needs to provide continuous, steady power for up to, let’s say, fifteen minutes, but a bare minimum of ten.”

Percy doesn’t even look up from the gun barrel he’s shaping, and as always, Tary’s cheeks warm a little at seeing the intensity of his friend’s focus. “I assume you’ve tried combustion.”

“It’s, uh, not really safe for this application. I was using a simple wind-up arrangement, but the spring gets unwieldy pretty quickly. Have you done much work with gravitational potential energy?”

“Not really my field of specialty,” Percy says. “What are you using the piston for?”

It’s a question Tary knew would be coming, so he tries to keep his voice as even as possible. “Oh, it’s really more of a conceptual thing at this point. I’m just sort of trying to work out how something like this would go.”

“Well, you’ve clearly done some experimentation already, otherwise you could’ve just redesigned it around an existing energy source. Give me some context here: what size piston are we discussing?”

Tary’s glad Percy’s not looking at him to see the way his cheeks flush. “Oh, to get the power I need, I’d say about the size of your arm.”

“Hmm, alright. Is it something that could be animal-powered?”

“ _Definitely_ not.”

Percy does look up then, and Tary forces himself to make eye contact. “Well,” Percy says, “if you’ve got a prototype, why not bring it into the shop?”

The truth is that the thing is bolted into the floor in his shop at home, down in the basement where Vex’ahlia never goes, but revealing that might bring on more questions. Besides, Doty can undo the bolts with relative ease. “Uh, sure. I’ll bring it in tomorrow.”

&&&

Even unbolted, the thing is unwieldy, so he has to have Doty carry it. Luckily the end of the piston built for… amusement is easily removed and stored inside the casing, so Doty doesn’t have to tote a large machine with an obvious phallus protruding from it through the middle of town.

As Doty sets it down in the workshop, Tary’s satisfied that it looks completely innocuous like this, no different from half a dozen other clockwork contraptions strewn around the room. As he’s opening the panels to expose the gears, Percy comes in, and from the flush on his face, Tary can tell he’s excited. In his hands is his Diplomacy glove.

“I was giving it some thought,” Percy says. “And I made a device for Diplomacy that converts electrical energy into chemical energy for storage. As a weapon, of course, it’s meant to discharge all that energy at once, but I’ve been toying with ways to release the energy on a slower, steadier basis. I haven’t perfected it yet, but it might be what you’re looking for.”

“That… that sounds perfect, actually.”

It takes some doing, hooking up the glove’s power source to the gear box, with quite a few false starts. The first couple of tries yield nothing, and the first time they succeed, a too-powerful surge of electricity knocks the piston into a table leg and sends the thing shooting across the room, dragging Diplomacy in its wake.

Tary sighs. “That’s why I usually bolt it down.”

“Easy enough to fix,” Percy says, rolling up his shirtsleeves and reaching for his heavier tools. Tary never misses an opportunity to watch him swing a mallet.

It takes the whole afternoon to fine-tune the thing, but when they’re finally able to get the energy flow right, the piston comes thrusting out in a steady, forceful beat. They both watch in silence for a moment, wary of another short, but it continues regularly for several minutes, neither slowing down nor emitting any smoke.

“I think we’ve done it!” Tary gasps, turning to Percy to celebrate.

Percy, whose eyebrows are now rising to his hairline as he watches the machine work. “Tary,” he says slowly, “what did I just help you build?”

“Uhhhh,” Tary says, laughing nervously and going to disconnect Diplomacy. “I told you, it’s mostly just a proof of concept. I wanted to see if I could steadily power a single piston, so maybe I could work next on a series of pistons, which could potentially—”

“Because I think this would make an excellent fucking machine.”

Tary thinks _Excuse me, but I’ve been calling it Darrington’s Devastating Auto-Dickinator_. But he says, “What?”

“Look, you attach a dildo to the end of the piston here,” Percy says, voice starting to rise with excitement. “Obviously it would take some careful adjustment and positioning, but you’ve really got something with that steady, long-lasting energy source. It could keep going with the same pace and amount of force much longer than any person could, not to mention the aim would be dead-on with every thrust. I can’t believe you didn’t think of—”

He looks up just then, and whatever he sees on Tary’s face stops him cold. “My gods,” Percy says, a smile starting to spread across his face. “You knew _exactly_ what you were making, didn’t you? Have you tried it?”

Tary’s mouth falls open, but no sound comes out.

“I’ll take that as a yes, then. How was it? Oh, of course, the wind-up mechanism wasn’t giving you much longevity. I’m sure that was frustrating in the extreme.”

A sound much like the air being let out of a bagpipe makes its way out of Tary’s mouth.

“Come on then, no need to be shy. We may have fixed that problem now.”

Tary shuts his mouth and tries to swallow. It’s only partially successful. When it becomes apparent that he’s not going to be so lucky as to burst into flames and thus not have to answer any of the preceding questions, he says, “Frustrating… is one word for it.”

Percy’s grin gets wider. “Well, now that we’ve fixed it, shouldn’t you try it again?”

Tary’s not sure he remembers saying yes, but a few minutes later when he’s removed the dildo attachment from the compartment, shown Percy how to fasten it on, and given himself a perfunctory fingering with lubricant, he can honestly say he’s never been so excited and so ready to vomit in his life.

Percy’s frowning at the machine, which he’d already bolted such that the piston sticks out to the side of the device. “Should I have secured it so the piston thrusts up?”

“Ah, no, no,” Tary says, trying to keep his voice at a normal octave as he withdraws his fingers from himself. “I found that, uh, my legs weren’t always sufficient to keep me upright. On its side, it is… customized to my height.”

“Ah, perfect!” Percy exclaims. Tary’s cock, which has so far remained mostly soft due to nerves, gives a twitch.

Percy thoughtfully lays down some dropcloths to cushion Tary’s hands and knees from the rough stone floor. He’s bustling about excitedly as though this were simply another of their many tinkering experiments, which is the only reason Tary can even think about doing this. Tary’s still mostly dressed, only his trousers pulled down to his knees, when he sets up in front of the machine.

“Th-this is the awkward part,” he says, reaching behind himself to get the dildo into place. He presses back gently until just the tip breaches him, and the nervous fluttering in his stomach starts to feel a little more like excitement.

Meanwhile, Percy is fiddling with Diplomacy and occasionally frowning thoughtfully in the direction of Tary’s bare ass. “Ideally, of course, we’d have some kind of regulator that would allow the user to modulate the flow of electricity and thus the pace of thrusting. I can try something like that here, but it won’t be terribly sophisticated. Just in case, you should probably be prepared to take a pounding right away.”

Yes, Tary’s cock definitely twitched at “take a pounding” in that refined tone of voice. Percy seems preoccupied with the glove, so Tary takes a quick moment to get a hand around his cock. He’s not fully hard yet, but being on display like this, in front of Percy’s critical eye, is doing more for him than he’d imagined. It surely won’t take long before—

There’s a spark in the corner of his vision, and the dildo thrusts in to the hilt, knocking a grunt out of him. Without delay, it pulls back and plunges forward again. Then again.

“Oh, pardon me,” Percy says. “I hope you were ready.”

“Yuh” is all Tary can manage.

As with his previous experiments, the first few strokes aren’t terribly comfortable. Tary’s very used to the size of the dildo, but the machine hasn’t got any of the finesse of a real person, and the start-up is always a little rough. Usually, he’d just stroke himself through it, but he’s not entirely sure what the protocol is with Percy here. Percy’s interest seems entirely mechanical, rather than sexual, and Tary’s not sure if he’s expected to display the same dispassion.

Soon, though, it isn’t going to matter what’s expected of him. What the machine lacks in finesse, it more than makes up for in stamina, and the steady, even drag of the dildo makes aloofness impossible. It is, after all, a machine designed to maximize pleasure, and Tary finds it hard to think scientifically while getting fucked.

“Okay,” Percy says after a moment. “I’m going to turn the power up.”

Tary has only a moment to think _it goes up?_ and ponder the relative power afforded by a wind-up spring versus electrical energy before Percy does something to Diplomacy and the dildo starts moving faster. And harder. Tary hasn’t put himself at the best angle yet, so the machine is merely providing a consistent source of stimulation rather than fucking him towards climax as quickly as possible. Still, a moan makes its way out of him before he can stop it, and he has to shut his eyes against the pleasure starting to build in his gut.

When he opens them, he sees that Percy has set Diplomacy down and is now… inspecting the piston. Closely. “Fascinating,” Percy murmurs, barely audible over the hum of the machine. “You’ve done an excellent job calibrating the piston and minimizing lateral movement.”

“Th-thank you.”

“And it’s maintaining a consistent thrusting force?”

It’s hard to see from this angle over his shoulder, but Percy’s eyes are wide, flicking back and forth between the machine and Tary’s ass. Tary bites back a groan. “Seems to be.”

Percy’s hand lands on the small of Tary’s back, and Tary jumps. It shifts the angle just enough that instead of gently brushing across Tary’s sweet spot, the dildo jams it head-on, and Tary yelps.

“Oh, sorry about that,” Percy says, but his hand stays firmly where it is. “Until we figure out the power modulation, it’s probably best to increase prostate stimulation gradually by adjusting the angle of your body.”

Yes, Tary would say he’s currently incapable of preventing himself from increasing prostate stimulation. It feels too fucking good not to. He hadn’t thought through the natural end result of this experiment, nor whether he wants to come all over the workshop floor with his friend ( _and crush, let’s be honest with ourselves, Tary_ ) looking on impassively. But he’s too weak a man to keep from angling his body so the dildo catches more and more of that bundle of nerves on each thrust. Either that, or he’s too much of a scientist not to see the experiment to its conclusion.

It crosses his mind that this is already past where he’d gotten in previous attempts. The wind-up mechanics would have long since wound down, forcing him to remove the dildo and shuffle around awkwardly until he could get to the crank. Now, though, the thing’s not stopping, just plunging into him unrelentingly without the need to rest or reposition, and it’s winding the spring in his own gut tighter and tighter.

Behind him, Tary hears, “I think I can get a little more juice out of it,” and the thing speeds up _again_. He can’t help it anymore – he’s moaning continuously now, unable to think or make words. All he needs is a hand on his cock and it’ll be over, but he finds himself frozen in place, fingers clenching helplessly into the cloth under his hands.

He’s staring down so intently, so focused on the feeling of the dildo pistoning in and out of him, that he’s totally taken off guard when a voice whispers in his ear, “Tell me, Tary, has it made you come before?”

Tary can feel the heat of Percy’s face just inches from his own, and as he speaks, his lips just barely graze the shell of Tary’s ear. “N-n-no,” he cries.

“And can you come like this, untouched, with nothing but a hard cock fucking you?”

Tary feels a tear slip down his cheek. “I d-d—I don—n-n—”

Warm lips press to his temple, and a slick, callused hand closes around his cock. It gives half a dozen firm, confident strokes before Tary’s gone, body seizing up as he comes. The machine doesn’t stop, doesn’t even slow down as he clenches around the thrusting dildo. It just keeps hammering away, ramming his prostate, fucking spurt after spurt of cum out of him until he’s wrung dry, the hand on his cock keeping pace.

It all goes from _amazing_ to _too much_ in the blink of an eye, and just as he cries out in overstimulation, the hand leaves him and the machinery behind him grinds to a halt.

He’s pretty sure he just collapses forward after that, face-first onto the dusty cloth.

An indeterminate amount of time later, strong hands help him onto his side. A damp cloth wipes his backside, and then he’s helped back into his trousers. When his mind clears, his head is pillowed on Percy’s thigh, a hand combing gently through his hair. “There’s no hope for your shirt, I’m afraid,” he hears. “I’ve sent Doty back to your house for another one, but I’m not sure he fully understood me. Odds are good you’ll get a new hat.”

_Oh gods. Doty_. “Was he,” Tary gets out weakly. “Was he taking notes?”

A pause. “You know, I honestly wasn’t paying attention.”

“That’s—that’s fair.”

“Well,” Percy says, his tone softer than Tary usually hears it. “There’s definitely some adjustments to be made, but I think that experiment was a success.”

Tary clears his throat. “You think?”

“Oh, definitely. I look forward to repeating it multiple times.”

**Author's Note:**

> I’ve fallen behind on replying to comments, but I just want to say that I’m treasuring every single one as if it were, say, my very own flying broom. I should have realized that, in doing this, I was essentially committing to Nano in October, but I had convinced myself “No, it’s cool, I can totally write a bunch of 500-word fics.” 40K words later… So, yes, you are all wonderful, wonderful people who are keeping me motivated on this delightfully weird journey, and I love you all!


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